Sound amplifier



Patented Apr. 23, 1929n 'UNITED STATES PATENT OFFICE.

SOUND AMPLIFIER.

Application led September 29, 1926, Serial No. 138,546, and in Germany October 2, 1925.

The invention relates to amplifiers for use in connection with speaking tubes, loud- I speakers for broadcasting purposes, gramophones and similar` sound reproducing machines, and more particularly to an ampliier ot' the horn type for. developing and modulating the sounds produced by the sound producing or reproducing instrument. I am aware that numerous attempts have been made heretofore to make amplifiers of the horn typez acoustically perfect in every respect, but as far as my knowledge goes, all such attempts for improving the timbre and quality of the reproduction and for eliminating harshness have been a failure inasmuch as hitherto nobody came to the idea of constructing an ampliiier or modulator to a certain degree or somewhat in the form of the human organ of speech comprising the relatively narrow throat or pharyngeal cavity, the relatively large cavity of the mouth or cavum oris land the yielding uvula. it have found that the tones and sounds produced by an amplifier or modulator constructed in accordance with this idea, are

absolutely faultless as regards the reproduction of the human voice since the conditions under which the sound-waves are propagated in my improved instrument are approximately the same as in the human organ of speech so that the tonality of the emitted soundsis thoroughly refined and tuned to the clear timbre of the human voice.

Accordingly, the object of my invention is to provide a sound reproducing and modulating instrument in which the soundwaves transmitted say by a diaphragm or the like, will be caused to pass through an elongated chamber or space which is comparatively small in diameter and then will be allowed to expand by entering into and passing through a chamber or space of a relatively great diameter, whilst at the transition point, that is the place of interconnection or communication between the two chambers or spaces, an elastic member adapted to vibrate is provided in imitation of the human uvula, so that the sound-waves are elasticaliy throttled by the strangulat- 5o ing elastic member just ai the moment or at the place where they expand and pass over to the chamber or space of greater diameter the said embodiments in a mere diagrammatic manner:

Figure l is a view in longitudinal section of the device constructed in accordance with my invention;

Figure 2 is a cross-section of the same;

Figure 3 is a view in longitudinal section of a modified construction of the device.

Before proceeding to describe in detail the several embodiments shown in the drawings I wish to admit that it is known in connection with loud speakers to provide a dialphragni in front of a concave mirror, in

structures of this kind, however, the diaphragmY prevents the sound-waves from passing out readily. In the amplifier constructed according to my invention, there is no obstruction in the emitting chamber and the sound-waves have perfectly free egress towards the aring mouth of the chamber in the full sectional area thereof.

Referring now to the drawings, in the embodiment shown in Figures l and 2 the letter a indicates a sound producing diaphragm belonging to the tone arm of a phonograph or any other suitable sound reproducing machine, but it goes without saying that in case of a speaking tube or the like.I as above intimated, any such interniediate'auxiliary means for transmitting the sound of the human voice will be dispensed with. In the embodiment shown the sound-waves emitted from the diaphragm at pass through an elongated chamber shaped to form a taper stem or tube I) with a bellow or swell c at the tiaring or larger end thereof. Integral with the inner wall of the swell c there is provided a small elastic band (l shaped and adapted to vibrate freely. In the sectional View shown in Figure 2 it will be seen that the said elastic band extends across a passage e and comprises two vibratory uvular formations or tongues projecting into the plane of interconnection between the taper tube t) and an expansion chamber f of greater diameter than that of the widest or flaring end of the truncated conical tube Zi. Instead of two tongues or uvulars d obviously a single one only may he provided and will give satisfactory result-s in some cases.

The chamber f is the amplifying space or room, properly speaking, and may be of any appropriate shape such as a truncated cone, a truncated ovoid or elliptoid body, and the like. At any rate the mouth chamber f mustbe considerably greater in diameter than the widest end of the conical tube Z below the pocket c partially closing the latter.

The depending vibratory band projects inwardly at the point or place ot' connection between the conical tube b and the mouth chamber f, the latter extending in a plane or on an axis perpendicular to the plane or axis of the conical tube I), las will be clearly seen in Figure l, and the passage e between the conical tube and the expansion or mouth chamber' is narrowed by the interpositiou of the vibratory uvula d, so as to form a throttling port.

As'regards the operation of the device it will be seen that the sound-waves passing through the conical tube are stopped and dammed in the pocket c and compelled to change their direction of movement so as to travel through the restricted passage e into the wider mouth chamber f, where they expand before they are emitted through the orifice thereof into the open air. It is a special purpose of the pocket c to prevent the sound-waves confined therein, from leaving the'conical chamber or tube Z) simultaneously or in regular order it being 'rather intended to shift and displace the same with relation to eachother and in pe riodic respects ere they are allowed to pass from the conical tube b over into the wider mouth chamber In this way the usually dull sound of the ampliiiers as hitherto constructed will be avoided and the tonality of the emitted sound-waves will be given a somewhat more plastic or musical character and, on the other hand, the provision ot the vibratory member or uvula al will assist in making the amplifier acoustically perfect in every respect, particularly by modulating the sound in strict similarity to the action of the human uvula, since the member (Z is designed to simulate the uvulaof the human throat I desire to have it understood that just the combination of a rigid pocket such as c with a resilient vibratory membersuch as d forming the iront wall or in :front thereof, and the co-operation of the two members of such combination with the result of relining and modulating the tone or sound to be amplified by the co-operation of a conical tube oi a relatively small diameter with an expanding chamber of relatively great diameter and which is disposed approximately at right angles to the former, is the essential novel feature oi' my invention, it being obvious, that ampliliers consisting of a smaller tube in connection with a larger tube or chamber of trumpet shape are old in themselves, whence follows that the ist of my invention resides in the hereinbe ore stated combination of members such as c and cl, either alone or in combination with a preferably trun'ipet-shaped amplifier.

Returning now to the drawings, the embodiment or modification illustrated in Figure 3 is ot' the saine general construction and arrangement as the embodiment depicted in Figure l, with the sole exception that the expanding or mouth chamber f in Figure 3 is trumpet-shaped with a gradually enlarged haring orilice g, whilst in Figure 1 the orifice g' is, to a certain degree, restricted and narrowed due to the contour inherent in a truncated hollow body of elliptoid or ovoid shape. Figure clearly' shows the restriction between the conical tube c and the mouth chamber f controlled by the vibratory yielding member d.

In general, it is to be understood that the forms shown and described are preferred embodiments of my invention but realizing that certain conditions will necessarily vary in concurrence with the adoption of my ampliier, I desire to emphasize the fact that various minor changes in the details ot' constructiom and in the proportion of parts may be resorted to when required without sacriticing any ot the advantages of my invention as delined in the appended claims` l.Vliat I claim isz An amplitier comprising a tapered tube, a swell partially closing the larger end of the latter to form a pocket, an eX- pansion chamber disposed substantially at right angles to the said tube and connected therewith, said chamber having an elastic vibratory band depending adjacent to said pocket so as to form a throttling passage between the said tube and the said expansion chamber.

2. A sound amplifier comprising a conical tube having an arched portion connected with and partially closing the larger end thereof, an expansion chamber having its walls connected to said arched portion and providing a passageway substantially at right angles to said conical tube, said chamber having an elastic uvularsshaped band afname depending from said arched portion at the junction of said tube and said chamber.

. 3. A sound amplifier comprising a tapered tube having an overhanging pharynxshaped portion partially closing the larger 'end of said tube, a sound emitting chamber having its Walls connected to said pharynxshaped portion and its axis substantially at right angles to the axis of said tapered tube,

RICHARD FRENKEL. 

